// 独一无二的
let s=Symbol();
console.log(typeof s);

let s2=Symbol();
console.log(s==s2);

// Symbol 不是类
let s3=Symbol('foo');
let s4=Symbol('foo');
console.log(s3==s4);


const o=require('./2.js');
// console.log(o);
//  如何向对象添加绝对不重复的key
let newObj={
    ...o,
    name:'ysw'
}


